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Technological University of the Philippines

Ayala Blvd., Ermita, Manila

College of Industrial Technology

Electronics Department

Assignment # 1

Muerong, Alancel S.

ECET/ 3/ B


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The History of Navigation

Navigation is the art of getting from one place to another, safely and efficiently. Wheneveryou find a store in a mall or walk home from school, you are using the tools of the earlynavigators. But what if you found yourself in a place you didnt recognize such as out inthe middle of the ocean?

The first record of boats large enough to carry goods for trade is around 3500 B.C. andthis would mark the birth of the art of navigation.These first navigators stayed close toshore and navigated by sight of landmarks or land characteristics that they could see.Usually they traveled by day and sought a calm harbor or anchorage at night. They did nothave charts but lists of directions, similar to todays cruising guides.

When they did venture out of sight ofland, the navigator was able todetermine his latitude (north/southdirection) by observing the height of

the sun during the day and the NorthStar at night.

Experienced mariners were said to plot their course by major constellations, though thiswas not an exact science. Vessels followed the east/west movement of the sun or thetrack of the stars. However, the navigator had no way to accurately determinelongitudeand therefore, once out of sight of land, had no idea how far east orwest he was. Estimates were made based upon the time it took to get there, asimple form ofdead-reckoning still used by navigators today.

Using this system, the navigator can determine the distance traveled from onepoint to another by multiplying the time underway by the speed of the vessel.

Since time was measured with a sandglass and speed was estimated bywatching pieces of seaweed pass by the hull, these early calculations were oftenway off.

Coastal navigators relied upon the sounding reed (c. Egypt 1500 BC) to measureshallow water depths and the wind rose which described the eight major winds attributedto their originating countries. Using a combination of depth soundings, the sun or stars andthe wind rose, these early navigators had to guess where they were when land could notbe seen.

The first ocean voyages were probably big mistakes a vessel blown off course by asudden storm or error by the helmsman. The Vikings regularly sailed to Iceland and

Greenland between 900 and 1000AD, apparently using only the sun, stars and wind astheir guide.

As brave as these early navigators must have been, they were also creative incompensating for their lack of technology. Floki Vilgjerdarsson, a great Viking explorercredited with the discovery of Iceland, carried aboard a cage of ravens. When he thoughtland should be near, he would release one of the birds. If it circled the boat withoutpurpose, land was not near, but if it took off in a certain direction, the boat followed,


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knowing the bird was headed toward land.

Of course, this only worked if the navigator could get close to land. (And not too close!)

One of the earliest man-made navigation tools was themariners compass, an early form of the magneticcompass(c.13

thCentury). Initially used only when the

weather obscured the sun or the North Star, these firstcompasses were very crude. The navigator would rub an ironneedle against a lodestone, stick it in a piece of straw andfloat it in a bowl of water. The needle would point in anortherly direction. Early mariners found the compassinconsistent most likely because they did not understandthat it pointed to the magnetic north pole, not true north (Thisis calledvariation). At the time, they could not explain thesevariations and could not put much trust in the readings whennavigating an unknown area.

The most practical use of the compass at this time was to identify the direction of the windto help the navigator determine which of the eight winds on the wind rose they wereexperiencing. Even after the development of more modern compasses with pivotingneedles, until variation was understood and documented, the compass was not asvaluable to navigators as it is today.

Much more valuable, at the time, was the invention of the lead line(c.13

thCentury)., which was a tool for measuring the depth of water and the

nature of the bottom. This line was weighted with lead and had graduatedmarkings to determine sea depth. The lead was coated with wax to bring upsamples of the bottom. A method of navigating from one depth to another based

upon the condition of the bottom developed, with sailing directions from the14

thCentury reading "Ye shall go north until ye sound in 72 fathoms in fair grey

sand. Then go north until ye come into soundings of ooze, and then go yourcourse east-north-east." (72 fathoms is 432 feet!thats a long line.)

The development of better navigational tools was motivated first by commerce and trade,then by the riches of discovery. The Phoenicians and Greeks were the first of theMediterranean navigators to sail from land to land and to sail at night. Often theynavigated by bonfires set on mountaintops (the earliest known system of Aids toNavigation).


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At this time, mariners began to realize thatmaps would be helpful and began keepingdetailed records of their voyages that land-based mapmakers used to create the firstnautical charts called Portolan Charts (c.

13

th

Century). The charts, created onsheepskin or goatskin, were rare and veryexpensive, often kept secret so thatcompeting mariners would not have accessto this knowledge. What they lacked inaccuracy they made up for in beauty. Landsand ports on the chart were highly decoratedwith depictions of buildings and flags.

The size of the lands on the chart was more a reflection of their importance to trade routesthan their actual geographical size. The charts did not have latitude or longitude lines butdid have compass roses indicating bearings between major ports. They were, of course,

not very accurate because the ability to measure distances at sea had not yet developed,nor was there an accurate method to portray the spherical surface of the earth on a flatpiece of material.

Mariners at this time also used the cross-staff andthe astrolabe (c.1484 Martin Behaim) to measure the angleabove the horizon of the sun and stars to determine latitude. Theforerunner of the much more portable (and accurate) sextant,the astrolabe was used to measure the altitude of a sun or star.Heavy and clumsy, it was very difficult to use aboard a rollingship, however, when new land was discovered and the astrolabetaken ashore, it was valuable in fixing the approximate latitude ofthe new discovery.

The hazards of sea travel during this time are clearly illustrated by Columbus' experience.His journal reveals that he did not even know how to calculate latitude properly, hisdeterminations being far too high. And like all sailors at the time, he was unable tocalculate longitude. When he encountered the Americas he actually thought he hadreached India which explains why the names Indies and Indians are still attached to thelands he found.

After a few weeks at sea the inaccuracies in the clocks could produce an error in longitudeof thousands of nautical miles. It is likely that the best clocks at the time lost 10 minutes aday which translates into an error of 175 miles. This daily loss was not consistent, so itcould not be compensated for.


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A major advance that made dead-reckoning much more accurate was theinvention of the chip log (c.1500-1600). Essentially a crudespeedometer, a light line was knottedat regular intervals and weighted to

drag in the water. It was tossedoverboard over the stern as the pilotcounted the knots that were let outduring a specific period of time. Fromthis he could determine the speed thevessel was moving. Interestingly, thechip log has long been replaced byequipment that is more advanced butwe still refer to miles per hour on thewater as knots. Using the sun and thestars, the navigator knew his beginningand ending latitude now he coulddetermine the distance he had traveledto estimate his east/west position.

The first accurate representation of the spherical earth surface wastheMercator Projection (Gerardus Mercator 1569). Of great value tonavigators because a compass bearing could be shown as a straightline (and they could, therefore, sail the shortest distance between twopoints), but the problem of determining longitude delayed the use ofthese charts for some seventy years after they were introduced.

In 1701, charts of magnetic variation in different parts of the worldwere available, making the magnetic compass a valuable (andconsistent) navigational tool.

But the key to determining longitude (how far east or west they were located) lay in theinvention of an accurate time-keeping device. It had long been known that the earth was aglobe and rotated one complete revolution in relation to the sun every 24 hours.Navigators knew that the sun reached its maximum altitude at noon, no matter where onearth they were. If they could determine what that exact time was on the longitude of 0they could easily calculate the longitude of their present position by the difference in thetwo times (one hour equaling 15of longitude).

This was considered so important that countries offered prizes for theinvention of an accurate chronometer. The British prize was wonby John Harrison in 1764 for his seagoing chronometer accurate toone-tenth of a second per day. James Cook used Harrisonschronometer to circumvent the globe and when he returned in 1779 his

calculations of longitude based upon the chronometer proved correct towithin 8 miles. A scientist and accomplished surveyor, Cook completedsuch accurate and detailed charts during his voyage that he changed

the nature of navigation forever and charts were rapidly developed around the world.

In 1884, by international agreement, the meridian of Greenwich, England was adopted asthePrime Meridian (0). Prior to that, all of the seafaring nations had their own primemeridians, causing longitude to be different on charts created in different countries.


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The ships chronometer remained an expensive but necessary navigation tool until radiosignals became universal, then a plain old wrist watch was all that was needed tocalculate longitude with accuracy. The radio receiver provided a continuously updatedtime signal from the Prime Meridian in Greenwich, England.

The 20th

century has seen advances in navigation tools beyond anything Columbus might

have imagined. The impetus for these developments was no longer trade and exploration,but for use in war. However, many of these instruments and technologies have beenadapted for peacetime use. We have become so dependent on these electronicinstruments that most recreational boaters today dont know how to plot a dead-reckoningcourse.

In 1907 Elmer Sperry introduced the gyroscopic compass which is unaffected byvariation or deviation as it points to true north, not magnetic north.

British physicist Robert Watson-Watt produced the first practicalradar(radio detection and ranging) system in 1935. It is used to locateobjects beyond the range of vision by projecting radio waves against them.Radar can determine the presence and range of an object, its position in

space, its size and shape, and its velocity and direction of motion. In additionto its marine uses, it is also used for controlling air traffic, detecting weather patterns andtracking spacecraft.

The hyperbolic navigation system knownas Loran (Long RangeNavigation) was developed in the U.S.between 1940 and 1943. It uses pulsed radio transmissions frommaster and slave stations that are received onboard andrecorded as small waves on the screen of a cathode-ray tube.The distance between the waves corresponds to the difference intime between the arrival of the signals from the two stations. Thisdifference is represented by a curve (hyperbola). Another set ofloran transmitters repeats this process and position is determinedby the intersection of the two curves called loran lines of position.

Accuracy ranges between a few hundred meters and a few kilometers. Used mainly by USships it is an expensive system with a limited coverage area and will ultimately be phasedout in favor of a newer, more accurate navigation system called GPS.

GPS (Global Positioning System), initiated in 1973, is operatedand maintained by the U.S. Department of Defense. This space-based radio-navigation system consists of 24 satellites and providesaccurate positioning to within about 30 feet as well as velocity and timeworldwide in any weather conditions. GPS works the same way asLoran (time difference between separate signals) but the signals comefrom satellites. Because you can receive GPS signals using small,inexpensive equipment it is being used in many new applications.


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NAP-Section

b) Early Navigational Instruments

Other ancient orientation methods and tools were

more sophisticated and elaborate. An example is

the latitude hook - a pretty simple device but very

useful and practical for its time. The Pacific

peoples began sea exploration in about 800 A.D.,

travelling east into the Pacific and eventually

settling many islands in the ocean. In their

adventures, they sailed with canoes and used a few

navigation devices at a time when most European

seamen kept close to shore and rarely ventured

into the open sea (with the exception of the

Vikings who used a sundial for their ventures into

the Atlantic ocean). The Pacific people used the

latitude hook for sailing from one island to

another, if both were on the same latitude. The

navigational device consisted of two bamboo

pieces. One of them was split, with a hook at the end. The other was a shorter bamboo

stick (a pointer). The two were tied to one another at a right angle. The latitude hook

worked because the stars appear to rotate around a fixed point in the sky - the celestialpole. In the northern hemisphere the celestial pole is Polaris - the North Star. At any

given time at night the Polaris remained at approximately the same point in the sky.

The latitude hook took advantage of this pointer and measured the angle between the

Polaris and the horizon. The hook was held at arms length, aligning the pointer with

the horizon. If the seaman could see Polaris through the hook of the perpendicular

bamboo piece, he knew that he was keeping course in the same latitude in which he

started his trip.

Another very simple device was used by the Arabs in their trade voyages around the

Indian Ocean. Travelling in dhows (see History), the Arab mariners made use of a

simple tool called "kamal" (meaning "guide"). The kamal consisted of a small woodenboard with a hole drilled in the middle of it, and a knotted string that passed through

the hole. The different lengths of knotted sting corresponded to different latitudes or

certain key ports and way-points previously described by Arab seamen. It worked on

the same principle as the latitude hook, but was more accurate since the string kept the

board at a fixed distance from the navigator's eyes. The string was also what allowed

this instrument to be used for a variety of latitudes, unlike the hook.

"Morski Sviat" magazine, permission obtained


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The "astrolabe" or "star-taker" -is a significantly more elaborate navigation tool and is

said to be the first scientific instrument used for navigation. It is believed that the

astrolabe originated in ancient Greece and was later "refined" by the Arabs into a

more sophisticated device - highly artistic and ornamented. But the older and plainer

astrolabe was the original tool. It was a disk with degrees of arc around its

circumference and sight vanes on a rotating pointer called"alidade." The disk wasmost commonly made of brass and was vertically hung from a ring. The navigator

would hold the device by that ring and raise it above his head. Then he would align

the alidade, so that the star or planet he is measuring by, could be seen in a straight

line - through both pinhole sights in the sight vanes. The angle of this line of view was

then read by the alidade and converted into latitude.


The quadrant is another instrument which seamen adapted for navigation. Its namecomes from the quarter-circle that it uses as a scale. The simplest quadrants are made

of a 90-degree protractor with a plumb weight hanging from its vertex. Astronomers

were the ones who took full advantage of the instrument and the Arabs were, again,

among the peoples who were quite familiar with the device. Instead of degree

measures, some of the ancient quadrants had names of major ports written on the

appropriate spots around the arc. When the cord hanging from the vertex cut the arc at

the name of a certain place, the sailor knew that he had to turn east or west along that

latitude line in order to reach that certain port. The readings of the quadrant were

taken by two people - one to take the instrument and look at the celestial body of

reference, and the other to read the altitude from the arc. In rough weather it was very

hard to take a reading on this device since the instrument had to remain steady for an

accurate reading. However this is slightly offset as in harsh weather visibility is

usually poor and astronomical instruments couldn't be used in the first place.

In daylight times, navigators need to be able to orient themselves by the sun. The

astronomical ring is yet another rather simple device, relying on the sun, rather than

the stars, for its readings. It is simply a ring, as its name suggests. It consists of a


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circle hung from a ring. Gravity aligns the ring with the zenith (the highest point that

the sun reaches in the sky). A tiny whole in the ring (pinnule) allows a ray of sunlight

to shine onto the inside of the circle, which is graduated in a degree scale. Thus the

sun's altitude is recorded; from that, latitude can be calculated.


The Vikings had no compasses or other accurate and complicated devices fornavigation, but simply a variation of a sundial. They used these simple wooden

instruments for their long open-sea voyages to Iceland, Greenland, and probably even

as far as the North American continent. The sundial principle of keeping track of time

remained the main type of "clock" (along with sandglasses) used on ships until the

chronometer took over in the second half of the 1700s. The sundial was used to keep

track of sailors' duty shifts, of celestial observations, and helped determine ships'

speed. Later when clocks became available for ships to use aboard, sundials remained

in use - to roughly check the accurateness of the other clocks on board.

An old, very complex, and highly accurate clock was the nocturnal. It was a star

clock, meaning that it used the position of the stars to determine the phases of themoon, the lengths of days and nights, holidays, sunrises and sunsets, positions of the

sun relative to the zodiac, and even (some advanced nocturnal) calculated tides. The

first of these devices was developed in the 1200s and was used by Europeans as well

as Arabs. The nocturnal consisted of a sight, a pointer, and date and hour disks. They

were often crafted in brass and some were very elaborate. They remained the most

accurate clocks at sea (and on land, for a long time). They were in use up until the


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beginning of the 19th century - long after the chronometer was perfected into a most

accurate time keeping device. The only downside of the nocturnal was that it

depended on the Polaris and could not function in the southern hemisphere (where

Polaris was below the horizon) or in any other circumstances in which the star was not

visible.

Cross-staff Back-staff"Morski Sviat" magazine, permission obtained

The cross-staffis a tool that was used for centuries as an astronomers' tool before the

German mathematician and navigator Martin Behaim adapted it for celestial

navigation in the 1480s. The cross-staff, or Jacob's staff, was a long, square rosewood

or ebony staff, and a shorter crosspiece (transom), which slides up and down the staff.

The staff functioned in the following way: it was placed close to the eye and the

crosspiece was adjusted so as "to fill the apparent distance between Polaris or the sun

and the horizon.Then, by the position of the crosspiece on the staff, an angular

measurement was taken on the scale on the edge of the staff.

The first navigational instrument, whose creator's name is known for sure, was

the backstaff. An English explorer of the 16th century, John Davis, was impressed by

the cross-staff, but wanted to improve upon it, to avoid the error due to the "disorderly

placing of the staff to the eye." His 1590 device (also known as the Davis or English

quadrant) was so simple and accurate that it earned a place in navigation for over 200years.


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Though simple in its application, the device is

hard to describe. In just a few words though: it

was made up of three vanes (sight, shadow, and

horizon ) and a pair of arcs attached to a staff and

divided in degrees. The sight vane slides along the

sight arc just as the shadow vane slides along theshadow arc. The two arcs are part of two circles

with a common center. That center is found on the

horizon vane. The small arc measures 60 degrees

and the large one - 30, thus providing a maximum

zenith altitude of 90 degrees. In simpler terms, the

backstaff was an improvement over the cross-

staff, because it allowed the navigator to take the

measurement standing with his back to the sun (hence the name) and using the sun's

shadow. The glare from looking directly into the sun was thus avoided resulting in

greater accuracy.

An instrument that everyone recognizes as the "ultimate" navigational tool is

the compass. There are two main types of compasses - the magnetic compass, which

is most widely known, and the gyrocompass. The common magnetic compass was in

use as early as the 13th century, it uses one or more magnetic arrows pointing in

direction to the North Pole, using earth's magnetic fields.The gyrocompass, on the

other hand, is not affected by earth's magnetism. It uses a gyroscope which is a device

whose axel aligns itself parallel with the north-south line - earth's rotation axis. Thus a

gyrocompass always points north and is immune to any magnetism errors that a

conventional magnetic compass may suffer.The sextant is an instrument used to measure the angular distance between two

objects. By calculating the angular elevation of the sun or other celestial bodies, a

navigator can determine both his longitude and his latitude. The octant - the sextant's

predecessor - was invented in 1973 in England and America, almost at the same

time. In America Thomas Godfrey, associate of Benjamin Franklin, came up with the

device. In Britain John Hadley made the discovery. The octant was a double-reflecting

instrument using two mirrors. The sextant works on the same principle -

superimposingthe images of the two objects, the distance between which is measured.



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Octant


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Maps, compasses, astrolabes, and calipers are among the early tools used by ocean

navigators. In the modern era, these tools have been largely replaced by electronic and

technological equivalents.

Despite these early beginnings, it would take many centuries before global navigation at

sea became possible. Until the fifteenth century, mariners were essentially coastal

navigators. Sailing on the open sea was limited to regions of predictable winds and

currents, or where there was a wide continental shelfto follow. Farther ventures were

enabled by the development of scientifically and mathematically based methods and

tools.

Early Navigational Tools

Determining latitude can be accomplished relatively easily using celestial navigation.

In the Northern Hemisphere, mariners could determine the latitude by measuring

the altitude of the North Star above the horizon. The angle in degrees was the latitude

of the ship.

Mariner's Compass.

One of the earliest human-made navigational tools used to aid mariners was the

mariner's compass, which was an early form of the magnetic compass. Early mariners

thought the mariner's compass was often inaccurate and inconsistent because they did

not understand the concept of magnetic variation, which is the angle between true north


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(geographic) and magnetic north. It was primarily used when the Sun was not visible to

help identify the direction from which the wind was blowing.

Nautical Charts.

During the mid-thirteenth century, mariners began realizing that maps could be helpful

and began keeping detailed records of their voyages. Thus, the first nautical charts were

created. These first charts were not very accurate, but were considered valuable and

often kept secret from other mariners. There was no latitude orlongitude labeled on

the charts, but between major ports there was a compass rose indicating the direction

to travel. (The term "compass rose" comes from the figure's compass points, which

resemble rose petals.)

Astrolabe, Sextant, and Chip Log.

Some of the early instruments used to assist sailors in determining latitude were the

cross-staff, astrolabe, and quadrant. The astrolabe dates back to ancient Greece, when it

was used by astronomers to help tell time, and was first used by mariners in the late

Tall ships keep alive the history of ocean navigation. Today, ships such as these call to

mind images of merchant ships from long ago and pirates in their heyday during the

eighteenth century.


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fifteenth century. It was used to measure the altitude of the Sun and stars to determine

latitude.

Around 1730, an English mathematician, John Hadley (16821744), and an American

inventor, Thomas Godfrey (1704

1749), independently invented the sextant. The

sextant provided mariners with a more accurate means of determining the angle

between the horizon and the Sun, moon, or stars in order to calculate latitude.

During the sixteenth century, the chip log was invented and used as a crude

speedometer. A line containing knots at regular intervals and weighted to drag in the

water was let out over the stern as the ship was underway. A seaman would count the

number of knots that went out over a specific period of time and the ship's speed could

then be calculated.

Longitude and the Chronometer.

Throughout the history of navigation, latitude could be found relatively accurately using

celestial navigation. However, longitude could only be estimated, at best. This was

because the measurement of longitude is made by comparing the time-of-day difference

between the mariner's starting location and new location. Even some of the best clocks

of the early eighteenth century could lose as much as 10 minutes per day, whichtranslated into a computational error of 242 kilometers (150 miles) or more.

In 1764, British clockmaker John Harrison (16931776) invented the seagoing

chronometer. This invention was the most important advance to marine navigation in

the three millenia that open-ocean mariners had been going to sea.

In 1779, British naval officer and explorer Captain James Cook (17281779) used

Harrison's chronometer to circumnavigate the globe. When he returned, his calculations

of longitude based on the chronometer proved correct to within 13 kilometers (8 miles).

From information he gathered on his voyage, Cook completed many detailed charts of

the world that completely changed the nature of navigation.

In 1884, by international agreement, the Prime Meridian (located at 0 longitude) was

established as the meridian passing through Greenwich, England.

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